CVE-2021-21257 : Vulnerability Insights and Analysis

This article provides insights into CVE-2021-21257, a vulnerability in Contiki-NG operating system versions prior to 4.6 that allows attackers to trigger out-of-bounds writes through the RPL-Classic and RPL-Lite implementations.

Understanding CVE-2021-21257

CVE-2021-21257 is a high-severity vulnerability discovered in Contiki-NG operating system versions before 4.6, exposing devices to potential out-of-bounds write attacks due to insufficient validation of the address pointer in the RPL source routing header.

What is CVE-2021-21257?

Contiki-NG, an open-source operating system for IoT devices, contained a flaw in the RPL-Classic and RPL-Lite modules that allowed threat actors to exploit out-of-bounds writes by injecting malicious packets into the network stack.

The Impact of CVE-2021-21257

The vulnerability poses a high severity threat, with a CVSS base score of 8.2, affecting the integrity of the system. Attackers can leverage this flaw to execute out-of-bounds writes, potentially leading to system compromise and unauthorized access.

Technical Details of CVE-2021-21257

The vulnerability originates from the rpl_ext_header_srh_update function within the rpl-ext-header.c modules, affecting both RPL-Classic and RPL-Lite. The issue arises from the unvalidated CMPR field value calculation within the source routing header.

Vulnerability Description

The flaw allows an attacker to trigger out-of-bounds writes at specific lines within the affected modules, potentially leading to unauthorized memory access and system compromise.

Affected Systems and Versions

Contiki-NG versions prior to 4.6 are impacted by this vulnerability, leaving devices running on these versions susceptible to exploitation.

Exploitation Mechanism

By injecting crafted packets into the network stack, threat actors can exploit the vulnerability to execute out-of-bounds writes, bypassing address pointer validation.

Mitigation and Prevention

It is crucial for users to take immediate actions to secure their systems and prevent exploitation of CVE-2021-21257.

Immediate Steps to Take

Users are advised to update their Contiki-NG installations to version 4.6 or above to mitigate the vulnerability. Additionally, implementing network segmentation and access controls can help reduce the attack surface.

Long-Term Security Practices

Maintaining up-to-date software versions, conducting regular security assessments, and monitoring network traffic for unusual patterns are essential for enhancing long-term security.

Patching and Updates

Users can apply the available patch for Contiki-NG 4.6 as a workaround until updating to the latest patched version to address the vulnerability effectively.